The invention concerns not only a process for the production of water-insoluble fibers of cellulose monoesters of maleic acid, succinic acid and phthalic acid, with an extremely high absorbability for water and physiological liquids, but also the fibers themselves.
There exists as before a need for water-insoluble fiber articles with improved absorbability in the areas of hygene, medicine, house keeping, clothing and technology. In particular it is desired that such special fibers are capable of being worked up with customary machines and production apparatus, which presupposes certain minimal values with regard to fiber strength and fiber elongation.
Hydrophilically modified viscous fibers are known under the commercial name Viscosorb (Lenzinger Berichte, Volume 51 (1981), pages 34 et seq.). Their water-retaining ability from 140 to 150% or 200 to 210% is indeed not an inconsiderable increase over normal viscose (80-90%). There appears, however, still a need for improvement.
Tolerable water-insoluble cross-polymerized fiber-shaped salts of carboxymethyl cellulose are known from DT-OS 19 12 740. They can display a water-retention value of more than above 300%. Indeed for these fiber-shaped salts to be only 5-16% soluble, the fiber-shaped water-soluble NaCMC-salts usually produced from cellulose must be cross-linked with epichlorohydrine or formaldehyde. The fiber-shaped condition of the final product results in other respects solely from the pre-given short fiber shape of the cellulose that is to be reacted chemically, which generally displays an average fiber length from 1-2.4 mm. The production of normal endless filaments with the aimed-for mechanical characteristics is naturally not possible in this manner.
Also known are cellulose acetophthalates, which are obtained from hydrolyzed cellulose acetate and an excess of phthalic acid anhydride in acetone or dioxane (Ullmann, First Edition, Volume 9, page 237). Herewith are produced esters of phthalic acid with a free carboxyl group. These products are suitable as water- or alkali-soluble textile finishings and are also employed as antistaticums in the coating of films.
The present invention is based upon the object of preparing new water-insoluble fibers, which particularly based upon their high and extremely variable absorbability for water and physiological liquids represents an interesting enrichment to the state of the art.